The invention relates to a shrinkage device for rapidly shrinking and outshrinking tools, especially hard metal tools, in so-called shrinkage tension chucks of paramagnetic or ferromagnetic materials using an induction heating coil.
A shrinkage tension chuck is understood to be a tool seat, for which the tool, which is to be held therein is held owing to the fact that initially the accommodating borehole of the shrinkage tension chuck, which is somewhat smaller than the shaft diameter of the tool, is expanded by being heated and the tool is then inserted, whereupon the chuck is heated once again, so that it contracts around the shaft of the tool, wedging it firmly. Conversely, the tool is removed once again by locally heating the surrounding chuck; because of the unavoidable transfer of heat also to the tool and, with that, of the simultaneous expansion of the latter, it is in most cases of decisive importance that the shrinkage chuck and the tool have different coefficients of expansion and that the heating takes place very rapidly. In the simplest cases, a naked flame or a hot air blower, with long heating times of the order of minutes, is used to heat the shrinkage tension chuck. Furthermore, the heating by heat transfer from a preheated metal piece, slipped over the shrinkage chuck, is also already known but, in practice, can be used successfully only for shrinkage chucks of small dimensions. In addition, the use of an induction heating coil in conjunction with the principle of inductive heating, which has already been known for decades, is also already known. In the latter case, the induction coil is pushed over the shrinkage tension chuck, remaining at a distance from the latter, in order to achieve contactless rapid heating.
It is an object of the invention to provide a shrinkage device with such an induction heating coil, which makes possible particularly rapidly shrinkage and outshrinkage of tools, even of different dimensions.
Pursuant to the invention, this objective is accomplished owing to the fact that a plurality of shrinkage chucks can be positioned on a turntable and brought from a position below the induction heating coil, which can be lowered, into a cooling position.
Due to the inventive use of a turntable, rapid shrinkage and outshrinkage can be achieved in a small space, since a heated shrinkage tension chuck, into which the tool is subsequently inserted, can be brought rapidly and simply into a cooling position for achieving the clamping effect and also, conversely, a cooled shrinkage tension chuck is always available, so that, after rapidly being shifted into the operating position below the induction heating coil, it can be heated up for accommodating a tool.
Particularly advantageously, the turntable has insertion seats, into which the shrinkage chucks with lateral cool air-supplying grooves can be inserted, through which cooling air can be blown from below past the shrinkage chuck inserted in the seats, so that the shrinkage chucks can be cooled by these means.
In this connection, it has proven to be particularly advantageous if guiding connecting pieces for the cooling air are fastened to the underside of the turntable and are opposite the outlets of a ventilator for the cooling air, there being no such outlets for cooling air below the position of the induction heating coil. When the ventilator is switched on, all shrinkage chucks, which are disposed in the insertion seat but do not lie below the induction heating coil, are then cooled constantly.
In order to be able to use the inventive shrinkage device for the shrinkage and outshrinkage of tools of any dimensions, provisions can be made in a further development of the invention that the insertion recesses of the cooling plate, formed to correspond to the diameters of the largest shrinkage tension chucks used, are surrounded by recessed, offset shoulders for inserting adapter rings providing a fit for the respective shrinkage chuck.
In a corresponding manner, air-conducting sleeves, which can be inserted preferably in the recesses of the turntable surrounding the adapter ring shoulders, taper conically in the upward direction. Over these air-conducting sleeves, the cooling air, blown upward over the cooling air guiding grooves, is passed selectively close past the heated conical upper parts of the shrinkage tension chuck, so that optimum utilization of the cooling air is ensured.
When such cooling air sleeves are provided, the formation advantageously is such that they end below the angular flange of the inserted shrinkage chuck, forming a support for the induction heating coil. By these means, the induction heating coil, which has been pushed on, can function as a counter-holding device, so that, when the tool is pulled out of the heated shrinkage tension chuck, the latter is not also lifted from the turntable in the event that a slight clamping action still exists.
In order to be able to bring the induction heating coil particularly rapidly and simply into the operating position and, for the purpose of rotating the turntable further once again into an upwardly displaced non-operating position, provisions can be made in a further embodiment of the invention that the induction heating coil is fastened to a supporting arm, which can be displaced vertically at a guiding column, disposed laterally next to the turntable. Preferably, the supporting arm is connected with a counterweight within the hollow guiding column by means of a cable control, which is diverted at the upper end of the guiding column over a roller. By means of this counterweight, the supporting arm can be shifted easily over rollers, without having to provide special locks, for holding the supporting arm in a raised position. Preferably, the guiding column should be surrounded by divided bellows, which are fastened to the top and bottom of the supporting arm and hide the cable control.
Moreover, it has proven to be particularly advantageous that the supporting arm has supporting legs for rollers lying against the guiding column, the supporting legs surround the guiding recess for the supporting arm, are elastic at least partially and adjustable by set screws and are disposed in a horizontal plane. The supporting legs can be constructed particularly simply by slots formed in one piece at a frame part inserted in the guiding recess of the supporting arm. In accordance with a particularly preferred embodiment of the invention, four supporting legs, lying against the four sides of the square guiding column over rollers, are disposed at the top and four at the bottom of the guiding recess.
Finally, it is also still within the scope of the invention that the supporting arm is provided with a cooling blower, which conducts cooling air, which is aspirated from the end of the supporting arm lying opposite to the induction heating coil, about the inductive heating coil, and permits it to emerge once again through slots in the wall of the supporting arm surrounding it at a distance. The inventive shrinkage device can also be used for demagnetizing tools passed through the induction heating coil by drastically reducing the frequency and voltage, which can easily be accomplished when producing the supply voltage for the induction heating coils by means of a.c. converters, for example, to a frequency of 50 Hertz and a voltage of 5 volts.
Moreover, the shrinkage times can also still be approximately halved if the induction coil, preferably formed as a ceramic coil, is adapted to the shape of the tension chuck, that is, to the conical part of the latter for accommodating the tool and, by these means, a tighter magnetic coupling is obtained. Moreover, it is still also within the scope of the invention for monitoring the temperature and switching off the converter at excessively high temperatures, to glue a switch on the ceramic coil, which preferably should be provided at the bottom with an exposed edge for counter-holding during outshrinking. The fact that it is seated directly on the ceramic coil and not on the plastic head has proven to be significantly more advantageous.
Further advantages, distinguishing features and details of the invention arise out of the following description of an example as well as from the accompanying drawings.